I am getting this error message if I put outdoorking-forum.com.au into browser:
Parse error: syntax error, unexpected token "[" in /home/xxxx/public_html/libs/smarty/sysplugins/smarty_internal_template.php on line 196
Again, this is due to the custom coding of scripts in your web root; your UBB.threads software is located in /forums which is working fine.
https://www.outdoorking-forum.com.au/ running non-UBB.threads stock code
https://www.outdoorking-forum.com.au/forum/ running UBB.threads
Read your paths:
/home/xxxx/public_html/libs/smarty/sysplugins/smarty_internal_template.php
This is not pulling code from the forum folder. It's likely a non-PHP8 version of Smarty being utilized (likely smarty 3.1.xx, the newer versions of smarty included in UBB.threads8 lacks a sysplugins folder (which your error is having issues with).